Wednesday, June 05, 2013

The Physics Of Toasty Buns

At high temperatures -- about 400 degrees and up -- a substantial part
of the heat that reaches the food arrives in the form of infrared light
waves rather than via hot air or steam.

The higher the
temperature, the bigger the part that radiant heat plays in cooking. But
this form of heat interacts with color in a profound way.
.
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A silvery, mirror-like fish skin is even more reflective than a white
car. About 90 percent of the radiant heat striking it simply bounces
away. Because only around 10 percent of the energy sinks in and warms
the fish, cooking initially creeps along slowly but steadily.

That
changes rapidly, however, as soon as the food gets hot enough to brown.
It's like changing from a white shirt to a black shirt on a sunny
summer day.

As the food darkens, that 10 percent of energy
absorbed rises by leaps and bounds, and the temperature at the surface
of the food soars.